Spiral bimetal operated coolant level switch



SPIRAL BIMETAL OPERATED oooLANT LEVEL SWITCH Filed Jan. 2e, 1965 Dec.20, 1966 M. T. CARLSON 2 Sheets-Sheet 1 70 f1.5' G f8 INVENTOR. MV/N 7.'CARLSON Mp4/M ATTORNEV De- 20, 1966 M. T. CARLSON 3,293,391

SPIRAL BIMETAL OPERATED COOLANT LEVEL SWITCH Filed Jan. 26, 1965 2Sheets-Sheet 2 INVENTOR. MARl//N 7.' CARLSON Elim@ f90/M ATTORNEY UnitedStates Patent O 3,293,391 SPIRAL BIMETAL OPERATED COOLANT LEVEL SWITCHMarvin T. Carlson, Anderson, Ind., assignor to General MotorsCorporation, Detroit, Mich., a corporation oi' Delaware Filed Jan. 26,1965, Ser. No. 428,121 7 Claims. (Cl. 200-113) This invention relates toelectrical switches and more particularly to a spiral, bimetal operated,cooltant level switch.

It is an object of the present invention to provide an improved Huidlevel switch that utilizes a heated bimetal immersed in the fluid whoselevel is to be monitored.

It is another object of the present invention to provide an improvedfluid level switch wherein a spiral-shaped bimetal is utilized toprovide the movement of a contact member during a switching action.

It is still another object of the present invention to provide animproved electrical `switch that is responsive to the temperature of acoolant in an engine cooling lsystem to provide a visual indication fora vehicle operator of a low coolant level.

Further objects and advantages of the present invention will be apparentfrom the following description,

yreference being had to the accompanying drawings wherein a preferredembodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a diagrammatic illustration of the electrical circuit inwhich the subject invention is used, the invention being shown in anoperative environment;

FIGURE 2 is a plan view of the subject invention, illustrated with partsbroken away, thereby exposing the interior portion of the subjectdevice;

FIGURE 3 is a sectional view of the subject invention taken along line3-3 of FIGURE 2;

FIGURE 4 is a sectional view of the subject invention taken along line 44 of FIGURE 2.

Referring now to FIGURE 1, a switch body, generally designated by thenumeral 10, is illustrated in a typical mounting position on anautomobile vehicle engine wherein a portion of the switch extends intothe cooling system of the engine. A battery 12 has one terminal groundedand another terminal conductively engaging a terminal 14 of the switch10 through an ignition switch 16. A terminal 18 of the switch 10 groundsan indicating lamp 20 through the switch body. It is understood that theswitch body is grounded to the vehicle engine.

Referring now to FIGURE 3, the terminal 14 is illustrated as beingcarried by a non-conductive portion 22 of the switch body 10. Theportion 22 is formed integrally with the base of the switch and iscomposed of any well-known insulating material. A conductive rivet 24firmly holds the terminal 14 engaged with the portion 22 and engages aconductive strip 26 on an opposite end. The conductive strip 26furnishes a conductive path between the rivet 24 and a spiral-shapedbimetallic element 28. In FIGURE 3 it is seen that the bimetallicelement 28 is suspended below the level of a fluid 30 carried in a fluidpassage 32 of the vehicle engine.

Referring to FIGURE 4, the bimetallic element 28 is carried by aconductive post 34 which is secured to 3,293,391 Patented Dec. v20, 1966ICC the bimetallic element at 36 so as to be non-rotatable with respectthereto. The conductive post 34 has a diameter 37 carried in an aperture38 in the non-conductive portion 22 of the switch body 10. A diameter 40of the conductive post 34 is carried in an aperture 42 in the portion 22of the switch body 1 0. It is clear that the side of the aperture 42provides a bearing surface for the conductive post 34 as it rotatesduring a switching action to be hereinafter described. A smallerdiameter pocket 44, formed at the base of the aperture 42, is arrangedto receive a sealing O-ring 46. The O-ring 46 is composed of anywell-known elastomeric material and serves the dual purpose of providinga seat for the flat portion 48 of the post 34 disposed between thediameter 40 and the diameter 37 as well as sealing the cornpartment 50from the fluid 30 in the cooling passage 32.

A resilient conductive member 52 is arranged to rotate with theconductive post 34, being secured thereto, and includes outwardlyprojecting resilient legs 54 and 56. The leg 54 is adapted to maintaincontact with a conductive wall 58 of the switch body 10 while the leg 56is adapted to slide on the conductive wall 58 and selectively engage acontact rivet 60 which in turn conductively engages the terminal 18. Itshould be noted that the contact rivet 60 is mounted in an insulatedmanner with respect to the conductive wall 58 by being enclosed in aplug 62 formed of any well-known insulating material. The terminal 18 isinsulatedly mounted with respect to the wall 58 by the insulating washer64 disposed between the terminal 18 and the wall 58. The

conductive post 34 is piloted at its upper end by a portion 66cooperating with a pocket 68 formed in the wall 58.

\ Referring to FIGURE 3, the switch body 10 is secured to a wall of thecooling passage 32 by means of bolts 70 compressing a gasket 72 betweenportions of the wall 58 and a wall 74 of the cooling passage 32.

Referring to FIGURE 2, the resilient conductive member 52 is illustratedas being connected to the conductive post 34. The leg 54 of the member52 is limited in its movement in one direction by an outwardlyprojecting ange 76 integrally formed with the wall 58.

- When the leg 54 is moved in a counterclockwise direction, as viewed inFIGURE 2, to a point where it engages the rivet 60, the leg 54 willsimultaneously engage the flange 76 to prevent any further movementthereof.

In operation, the ignition switch 16, illustrated in F-IG- URE 1, isclosed and power is thereby provided to the terminal 14 and to the lamp20. Referring to FIGURE 3, the power to terminal 14 is conducted throughthe rivet 24, through the strip 26, to the bimetal 28, and on throughthe conductive post 34, to the leg 54, to ground, as seen in FIGURE 3.The power thus provided heats the bimetallic element 28 and causes it tohave a tendency to rotate on the axis of the post 34,

stantially the position Ashown by the solid lines in FIG- URE 2. It isseen therein that they member` 52 is out of engagement with the rivet 60and, therefore, no current can llow through the ungrounded lamp 20.

When the temperature of the fluid 30 exceeds certain predeterminedlimits or the fluid in the passage 32 escapes, leaving the bimetallicelement 28 exposed, the tendency of the element 28 to ro-tate on t-heaxis of the post 34 will be realized, resulting in a movement of themember 52. 'Referring to FIGURE `4, it is seen that the fluid 30 lhas-receded below the depth to which the bimetallic element 28 is disposedand the leg 56 has moved strom the position shown in FIGURE 3 intoconductive engagement with the rivet 60. In this situation, a parallelcircuit is set up with the bimetallic element 28 still being heated andan Ialternate path for current flow provided through lamp 20, to theterminal 18, through the member 52 to ground. The lamp 20 is therebygrounded and becomes incandescent, alerting the operator of the vehicleto the tact that the temperature limits established for proper operationof the cool-ing system have been ex- 'ceeded .and maintenance isnecessary. It is understood that the particular temperature rangesestablished for satisfactory operation of the cooling system aredetermined -by the design, and an appropriately operative bime- `tallicelement 28 can be provided in a .given system to bring about the desiredresult.

T-he utility of the subject invention is extended due to itsresponsiveness both to a dropping of fluid level in a 'lluid chamberbelow the level of the bimetal as well as Ibeing responsive to the totalabsence of uid in the chamber. It is clear that the heat developed bythe bimetal 28 can be dissipated by the iluid 30 under normal operatingconidtions, but cannot be satisfactorily dissipated when the fluid levelreccdes or the fluid temperature exceeds predetermined limits.Therefore, the subject device can be utilized as a level sensingmechanism by v suspending the biemta'llic element 28 down to a minimumdetermined level in a fluid container. In this instance, the temperatureof the uid need not be controlling of the action of the bimetal, but theactual presence of the fluid surrounding the lbimetal is required inorder to gain the required dissipation 4of heat.

While the embodiment of the present invention as here in disclosed,constitutes a preferred form, it is to be understood that other yformsmight be adopted.

Wlhat is claimed is as follows:

1. A fluid level indicator comprising: a switch body; -rst terminalmeans carried through one wall of said switch body and adapted toconductively engage a power source; second terminal means carried in onewall of 4said switch body and adapted to electrically engage anindicator light, said se-cond terminal means having a conductive portionexposed within said switch body; Contact means pivotally supported bysaid switch body and including two outwardly projecting resilient legs,a first of said legs selectively engaging the exposed portion of thesecond terminal, a second of said resilient legs being arranged tomaintain a conductive relationship between said switch body and aground; and temperature responsive means carried by said contact meansand including a portion in conductive engagement with the iirstterminal, said temperature responsive means having means arranged topivot said contact means in response to a raising of temperature of afluid thereby moving a first of said outl wardly projecting legs intoconductive engagement with the second' terminal providing thereby aground for the -light connected thereto.

2. A uid level indicator tor use with an automobile engine coolingsystem, said fluid level indicator comprisl ing: a switch body adaptedto be mounted over an opening in the engine cooling system; a irstterminal adapted to electrically engage a power sour-ce and beingmounted through one wall of said switch body; a vsecond terminal adaptedto -conductively enga-ge an indicating device and being mounted throughanother wall of said switch body, said second terminal having aconductiveporticn exposed within said switch body; resilient contactmeans being pivotally supported by said switch body and including aportion projecting into thermal conductive Arelationship with iluid inthe vehicle cooling system, a portion of said contact means selectivelyengaging said second terminal and another portion of said contact meansbeing arranged to provide a ground 4for said first terminal thereby; andtemperature responsive means carried by a portion of said contact meansin the opening of the engine cooling system wherein a portion of saidtemperature responsive means is submerged in the lliuid therein andresponsive to the temperature thereof, said temperature responsive means'being heated by power through said rst terminal and thereby poised fordeflection, said temperature responsive means being normally cooled bythe lluid in lthe engine cooling system thereby preventing any deectionduring heating of said temperature responsive means, said temperatureresponsive means being delectable as cooling from the fluid in theengine cooling system is lost thereby rotating a portion of said contactmeans int-o conductive engagement with the second terminal therebycompleting an electrical circuit to the indicating device.

3. A duid level indicator accor-ding to claim 2 wherein rthe temperatureresponsive means is a spiral-shaped bimetallic element carried by saidcontact means.

4. The lluid level indicator according to claim 3 wherein thespiral-shaped bimetallic element is heated and controllably mounted byengaging the rst terminal, said spiral-shaped bimetallic element beingmounted at its center to said contact means.

5. A uid level indicator adapted for use with the cooling system ofvehicle engines, said indicator comprising: an indicator body adapted tobe mounted over an aperture in the engine cooling system; a rst terminaladapted to conductively engage a power source and be ing carried throughone wall of said switch body; a second terminal adapted to cond-uctivelyengage an indicating device and bein-g carried through one wall of theswitch body with a conductive portion disposed therein; said firstterminal 'being insulatedly mounted with respect to said switch body,said switch body being grounded through the vehicle engine; resilientcontact means being pivotally supported 'by a portion of said switchbody and including a portion suspended in the engine cooling system to alevel normally containing a iluid, said contact means Ihavirxg aresilient outwardly projecting portion selectively engaging theconductive portion of said second terminal `and havin-g a secondoutwardly projecting resilient portion slidably maintaining conductiverelationship to the grounded portion of the switch body; and temperatureresponsive means carried by the portion of the contact means suspendedin the engine cooling system `and having a second portion conductivelyengaging said insulated first terminal, power from the power sourcebeing supplied to the temperature responsive means through the insulatedfirst terminal to ground, the heat generated thereby being normallydissipated by the -fluid in the engine cooling system, said contactmeans being selectively pivotable into conductive engagement with thesecond terminal when ll-uid reaches a level in the engine cooling systemwherein the heat is not dissipated from the temperature responsivemeans, said pivoting contact means energizing a circuit through thetemperature responsive means to the indicating device to alert a vehicledriver of a level in the engine cooling system below the suspendeddisposition of the temperature responsive means.

r6. The fluid level indicator according to claim 5 wherein thetemeprature responsive means is `a spiral-shaped bimetallic element heldat one end by the conductive engagement with the iirst terminal and held-at an opposite end by the portion of the contact means suspended in theliu-id of the engine cooling system, said temperature responsive meansbeing thereby pivotable on its own axis against the xed mounting to the'rst terminal.

7. The uid level indicator according to claim 6 wherein the Contactmeans is a conduct-ive element pivotally supported in a pocketintegrally forme-d with a Wall 5 of said switch body, said integrallyformed pocket having a multidiameter inner periphery, a smallestdiameter of which is arranged to receive -a bearing O-ring and sealingelement to support a langer diameter portion of the contact means in a[larger diameter portion of said 10 pocket.

References Cited by the Examiner UNITED STATES PATENTS 2,759,066 8/1956Short et al. 200-138 3,001,052 9/1961 Swanson 200-138 3,081,393 3/1963Wolhl 20G-138 BERNARD A. `GILHEANY, Primary Examiner.

T. MACBLAIN, Assistant Examiner.

1. A FLUID LEVEL INDICATOR COMPRISING: A SWITCH BODY; FIRST TERMINALMEANS CARRIED THROUGH ONE WALL OF SAID SWITCH BODY AND ADAPTED TOCONDUCTIVELY ENGAGE A POWER SOURCE; SECOND TERMINAL MEANS CARRIED IN ONEWALL OF SAID SWITCH BODY AND ADAPTED TO ELECTRICALLY ENGAGE AN INDICATORLIGHT, SAID SECOND TERMINAL MEANS HAVING A CONDUCTIVE PORTION EXPOSEDWITHIN SAID SWITCH BODY; CONTACT MEANS PIVOTALLY SUPPORTED BY SAIDSWITCH BODY AND INCLUDING TWO OUTWARDLY PROJECTING RESILIENT LEGS, AFIRST OF SAID LEGS SELECTIVELY ENGAGING THE EXPOSED PORTION OF THESECOND TERMINAL, A SECOND OF SAID RESILIENT LEGS BEING ARRANGED TOMAINTAIN A CONDUCTIVE RELATIVESHIP BETWEEN SAID SWITCH BODY AND AGROUND; AND TEMPERATURE RESPONSIVE MEANS CARRIED BY SAID CONTACT MEANSAND INCLUDING A PORTION IN CONDUCTIVE ENGAGEMENT WITH THE FIRST TERMINALSAID TEMPERATURE RESPONSIVE MEANS HAVING MEANS ARRANGED TO PIVOT SAIDCONTACT MEANS IN RESPONSE TO A RAISING OF TEMPERATURE OF A FLUID THEREBYMOVING A FIRST OF SAID OUTWARDLY PROJECTING LEGS INTO CONDUCTIVEENGAGEMENT WITH THE SECOND TERMINAL PROVIDING THEREBY A GROUND FOR THELIGHT CONNECTED THERETO.